Method for selecting rach freamble sequence for high-speed mode and low-speed mode

ABSTRACT

A method for selecting a RACH preamble sequence for a high-speed mode and a low-speed mode is disclosed. In the case of acquiring sequence-type information to be used by a specific UE contained in a high-mobility region, a signaling reanalysis method under a general circular shift condition is disclosed, and a method for acquiring sequence-type information via the signaling using the sequence set configured by a restricted circular shift condition is also disclosed. Finally, a method for constructing a sequence set is disclosed.

DETAILED DESCRIPTION OF THE INVENTION (DESIGN) 1) Object of the Invention (Design)

The present invention proposes a method for setting up a configuration set of a cyclic shift and a method for transmitting and detecting a cyclic shift value.

2) Description of the Related Art

Hereinafter, technical problems most recently disclosed on the present invention (design) will be described. Should any publication exist as one or more examples of the related art invention, any publication including documents or patent gazettes will be incorporated and will be described based upon the accompanying drawings using the same reference numerals.

(The accompanying documents are essential in drawing up the claims of the present invention (design).)

(1) Structure of the Related art

In a mobile communication system, there are times when diverse cyclic shift sizes of a specific sequence are to be supported. For example, in a random access channel, the size of a cyclic shift of a ZC-ZCZ sequence varies depending upon the size of each cell. It is assumed that the length of a ZC sequence is equal to N (eg., 839) and that M (e.g., 64) number of opportunities is to be always provided for each cell. Accordingly, in case of a cell having a small cell size and using only one root index, a sequence made of (M/1) (eq. 64) number of cyclic shifts for each root index should be provided. In a cell using K number of root indexes, a sequence made of ceil(M/K) number of cyclic shifts for each root index should be provided. As described above, various types of cyclic shifts should be provided depending upon the cell size, or depending upon the number of root indexes used for each cell.

(2) Description for Operation of Related Art Device

Table 1 shows a configuration of a cyclic shift set proposed in TI [1]. Herein, it is assumed that the length of a ZC sequence is equal to 863. Also, based upon an LTE working assumption, the number of opportunities for each cell is always set to support 64 opportunities. In a cell having a cell radius less than 0.78 km, 1 root index is used, and 64 opportunities are generated by 13 samples cyclic shift. In a cell having a cell radius within the range of 0.78˜2.59 km, 2 root indexes are used, and 32 opportunities for each root sequence, i.e., a total of 64 opportunities are generated by 26 samples cyclic shift. In a cell having a cell radius within the range of 2.59˜6.34 km, 4 root indexes are used, and 16 opportunities for each root sequence, i.e., a total of 64 opportunities are generated by 53 samples cyclic shift. In a cell having a cell radius within the range of 6.34˜13.85 km, root indexes are used, and 8 opportunities for each root sequence, i.e., a total of 64 opportunities are generated by 107 samples cyclic shift.

TABLE 1 Cell scenarios with different cyclic shift increments - baseline structure [1] # of cyclic Max. cell radius Sequence shifts per ZC # of ZC Cyclic shift from cyclic shift length (μs) seq. sequences (samples) (km) 800 64 1 13 0.78 32 2 26 2.59 16 4 53 6.34 8 8 107 13.85 [1] R1-063214, Non Synchronized Random Access Design for High Doppler Conditions, TI

(3) Problems of the Related Art

1. The Use of a Small Configuration Increases Complexity and Reduces a Reuse Factor

For example, let's consider the configuration where the cell radius is within the range of 6.34˜13.85 km in Table 1. In a cell having the cell radius slightly larger than 6.34 km, excessive cyclic shift samples are used. Thus, an excessive number of root indexes are used. Such usage of a larger number of indexes increases complexity in the sequence creation (or generation) and detection in the base station and mobile terminal (or mobile station) and also reduce the sequence reuse factor. In a cell having a cell radius within the range of 6.34˜13.85 km, instead of using 8 root indexes, if a variation of number of root indexes, such as 5, 6, 7, and 8 root indexes, can be used, then the above-described problem may be resolved.

2. The Use of a Large Configuration Leads to Signaling Overhead

Let's assume that the number of opportunities available to be used for each cell is equal to M. For example, based upon an LTE working assumption, the number of opportunities for each cell is always set to support M=64 opportunities. In this case, the cell may be designed to have M number of configuration sets. Depending upon the size of a cell, among M different types, each cell may use one type of root index (set) and cyclic shift. The above-described case of supporting all of the total number of opportunities leads to a signaling overhead. In order to notify information on M (eg., 64) number of opportunities, log 2(M) (eg., 6) bits are required. If the number of configurations can be reduced, the signaling overhead may also be reduced.

Therefore, the present invention proposes a method of setting an adequate number of configurations. Additionally, the present invention also proposes a method of reinterpreting the configuration, when using the restricted cyclic shift.

3) Description of the Present Invention (Design)

all overall description will be made in relation with resolving the object of the present invention (design)

(1) Structure of the Present Invention (Design)

The present invention proposes a method of setting an adequate number of configurations. Additionally, the present invention also proposes a method of reinterpreting the configuration, when using the restricted cyclic shift.

(2) Description for Operation of the Present Invention (Design)

In applying the present invention, there are no limitations in the number of indexes, information type, channel type, level depth, multiplexing type, channel coding type, and so on. An example of using a root index of a ZC seq. in a random access channel in a multiple cell will be given for simplicity. The root index of the present invention may correspond to a physical root index and may also correspond to a logical root index.

1. Method for Setting-Up Configuration

The configuration of a configuration set is available based upon the following process. For all possibilities of any one specific variable parameter, the required values for the associated parameter are calculated. When the associated parameters each indicate only one value, the corresponding variable parameter is selected. When the associated parameters coincide, among the coinciding variable parameters, only one or a small number of parameter values are selected based upon a specific rule. Such specific rule may include selecting the largest parameter value, selecting the middle parameter value, selecting the lowest parameter value, or selecting a parameter value of a specific order. The configuration set may be configured by using only parameters selected in the above-described process. Herein, only one of the associated parameters may be considered and selected, or multiple parameters may be simultaneously considered and selected. Each case will be described with examples in 1.1 and 1.2.

1.1 From View Point of Minimize Required Root Sequence per Cell

For example, let's assume that the length of a ZC sequence is equal to 839. If the number of ZC sequences used for each cell is equal to 22, the number of required cyclic shifts per sequence in order to support 64 signatures is equal to 3. If the number of ZC sequences used for each cell is equal to 31, the number of required cyclic shifts per sequence in order to support 64 signatures is also equal to 3. In other words, while the number of required cyclic shifts remains the same, the number of required ZC sequences required per cell may vary. And, accordingly, we can select and use one based upon a specific standard. For example, a minimum value may be selected in order to reduce complexity and to increase the sequence reusing factor.

The available configuration is set by the following order:

-   -   1. The maximum number of opportunities available for each cell,         or the minimum number of opportunities that are to be supported,         M is set.     -   2. When using 1 to M number of root indexes, the maximum number         of cyclic shifts required per root seq. for supporting the total         M number of opportunities is respectively calculated.     -   3. Configuration is set from the number of cyclic shifts per         root seq.         -   A. When only one cyclic shift exists per root seq., the             corresponding cyclic shift is set for the configuration         -   B. When different types having the same number of cyclic             shifts per root seq. exist, only the case of using the             smallest root index is set for the configuration, in order             to increase sequence reuse factor and to decrease the             complexity.

The number of random opportunities available for each cell in non-synchronized random access of a 3GPP TS 36.211 system is always fixed to 64. For access, the terminal randomly selects one of the 64 signatures, so as to access the base station through a RACH Slot. This opportunity will be referred to as a common or random signature. Apart from the common or random signature, a dedicated signature may be used for diverse purposes, such as handover, UL synchronization, E-MBMS user detection, E-MBMS feedback, scheduling request indicator, and so on. Such dedicated signature may correspond to a UE specific or UE group specific signature, or may correspond to a service specific signature. In this case, the number of opportunities in step 1 may be decided by considering only the common or random signature, or may be decided as an added number of the common or random signature and dedicated signature. Alternatively, the setting of two different configurations is also possible. An example of considering only the common or random signature will be given in the following description.

The example is as follows. It is assumed that the length of a sequence is equal to 839, and that the number of opportunities available per cell is equal to 64. In this case, a number of root indexes from 1 to 64 may be used. Therefore, M=64. The number of cyclic shifts for using 1-64 root indexes is respectively calculated as shown below.

No. of root per cell No. of cyclic shift per root cyclic shift (samples)

-   -   1 - - - 64 - - - 13 samples     -   2 - - - 32 - - - 26 samples     -   3 - - - 22 - - - 38 samples     -   4 - - - 16 - - - 52 samples     -   5 - - - 13 - - - 64 samples     -   6 - - - 11 - - - 76 samples     -   7 - - - 10 - - - 83 samples     -   8 - - - 8 - - - 104 samples     -   9 - - - 8 - - - 104 samples     -   10 - - - 7 - - - 119 samples     -   11 - - - 6 - - - 139 samples     -   12 - - - 6 - - - 139 samples     -   13 - - - 5 - - - 167 samples     -   14 - - - 5 - - - 167 samples     -   15 - - - 5 - - - 167 samples     -   16 - - - 4 - - - 209 samples     -   17 - - - 4 - - - 209 samples     -   18 - - - 4 - - - 209 samples     -   19 - - - 4 - - - 209 samples     -   20 - - - 4 - - - 209 samples     -   21 - - - 4 - - - 209 samples     -   22 - - - 3 - - - 279 samples     -   23 - - - 3 - - - 279 samples     -   24 - - - 3 - - - 279 samples     -   25 - - - 3 - - - 279 samples     -   26 - - - 3 - - - 279 samples     -   27 - - - 3 - - - 279 samples     -   28 - - - 3 - - - 279 samples     -   29 - - - 3 - - - 279 samples     -   30 - - - 3 - - - 279 samples     -   31 - - - 3 - - - 279 samples     -   32 - - - 2 - - - 419 samples     -   33 - - - 2 - - - 419 samples     -   34 - - - 2 - - - 419 samples     -   35 - - - 2 - - - 419 samples     -   36 - - - 2 - - - 419 samples     -   37 - - - 2 - - - 419 samples     -   38 - - - 2 - - - 419 samples     -   39 - - - 2 - - - 419 samples     -   40 - - - 2 - - - 419 samples     -   41 - - - 2 - - - 419 samples     -   42 - - - 2 - - - 419 samples     -   43 - - - 2 - - - 419 samples     -   44 - - - 2 - - - 419 samples     -   45 - - - 2 - - - 419 samples     -   46 - - - 2 - - - 419 samples     -   47 - - - 2 - - - 419 samples     -   48 - - - 2 - - - 419 samples     -   49 - - - 2 - - - 419 samples     -   50 - - - 2 - - - 419 samples     -   51 - - - 2 - - - 419 samples     -   52 - - - 2 - - - 419 samples     -   53 - - - 2 - - - 419 samples     -   54 - - - 2 - - - 419 samples     -   55 - - - 2 - - - 419 samples     -   56 - - - 2 - - - 419 samples     -   57 - - - 2 - - - 419 samples     -   58 - - - 2 - - - 419 samples     -   59 - - - 2 - - - 419 samples     -   60 - - - 2 - - - 419 samples     -   61 - - - 2 - - - 419 samples     -   62 - - - 2 - - - 419 samples     -   63 - - - 2 - - - 419 samples     -   64 - - - 1 - - - 839 samples

FIG. 1. No. of root per cell & No. of cyclic shift per root

The example shown in FIG. 1 shows a number of cyclic shifts required for each root index, when using 1 to 64 root indexes for each cell. When using 32 root indexes for each cell, 2 cyclic shift values are required for each root index in order to configure 64 opportunities. When using 63 root indexes for each cell, 2 cyclic shift values are also required for each root index in order to configure 64 opportunities. Therefore, the usage of 32˜64 root indexes per cell is not always required. By configuring 32 single configurations using the minimum number of root indexes, low complexity in creation and detection of sequences in the base station and the mobile terminal may be ensured, thereby being able to increase the reuse factor and to reduce signaling overhead.

The example shown in Table 2 corresponds to the result of selecting a configuration by selecting a combination having the same number of cyclic shifts as the lowest root index by using the results of FIG. 1. Herein, the maximum cell radius available for support from the cyclic shift samples has been calculated. The maximum cell radius has been calculated while considering a delay spread of 5.21 μs, and has also been calculated by considering a case of having no guard sample and a case of having 2 guard samples, respectively.

TABLE 2 Example of NSRA preamble cyclic shift values No. of ZC sequence No. of Cyclic shift per cell per ZC sequence Cyclic Max. cell radius [km] Configuration (no cyclic shift (no cyclic shift Shift No Guard 2 guard No. restrictions) restrictions) [samples] sample samples 1 1 64 13 1.1 0.8 2 2 32 26 2.9 2.6 3 3 22 38 4.5 4.2 4 4 16 52 6.5 6.2 5 5 13 64 8.1 7.8 6 6 11 76 9.8 9.5 7 7 10 83 10.8 10.5 8 8 8 104 13.7 13.4 9 10 7 119 15.8 15.5 10 11 6 139 18.6 18.3 11 13 5 167 22.4 22.1 12 16 4 209 28.3 28.0 13 22 3 279 38.0 37.7 14 32 2 419 57.4 57.1 15 64 1 839 115.8 115.5 16 reserved reserved reserved reserved reserved

When the total number of cyclic shifts for all root indexes used in the cell exceeds the number of opportunities that are to be supported for each cell, settings may be made so that only a specific number of cyclic shifts are used starting from the beginning for each root index, or settings may be made by alignment in an increasing order or a decreasing order so that the entire cyclic shifts can be used starting from the foremost root indexes, or settings may be made according to a specific standard (or format). For example, in Table 2, when using the configuration No. 3, the total number of opportunities is equal to 3*22=66 opportunities. At this point, if only 64 opportunities are actually used, the 64 opportunities may be selected by using a variety of methods. 22 opportunities may be selected from the first index, 21 opportunities may be selected from the second index, and 21 opportunities may be selected from the third index. Alternatively, 22 opportunities may be selected from the first index, 22 opportunities may be selected from the second index, and 20 opportunities may be selected from the third index. If a number of opportunities exceeding the basic number of opportunities is available in a cell, all 66 sets may also be used.

The last 16^(th) configuration has been marked to be reserved for the signaling of 4 bits. Such configuration may be decided in advance, or may be flexibly decided and used by the manufacturer (or provider). For example, a configuration may be additionally assigned to the portion having a greater cell coverage difference.

1.2 From View Point of Maximize Cell Radius

For example, let's assume that the length of a sequence is equal to 839. If the cyclic value is equal to 210, the number of ZC sequences required per cell so as to support 64 signatures is equal to 22. If the cyclic value is equal to 279, the number of ZC sequences required per cell so as to support 64 signatures is also equal to 22. In other words, a variety of cyclic shift values may exist while having the same number of ZC sequences required per cell, and one cyclic shift value may be selected based upon a specific standard. For example, a method of selecting and using the largest cyclic shift value for greater cell coverage may be used (4.B case 1). In another example, the case of using only the smallest cyclic shift value may be set as the configuration. When using this method, sequences having at least M number of opportunities may be generated (or created). In this case, the sequences exceeding the required M number of opportunities may be used for the purpose of a dedicated signature (4.B case 2).

The available configuration is set by the following order:

-   -   1. The maximum number of opportunities available for each cell,         or the minimum number of opportunities that are to be supported,         M is set.     -   2. The maximum available cyclic shift value is set by using the         sequence length.     -   3. When using each cyclic shift value of each number within the         given range, the maximum number of cyclic shifts required per         root seq. for supporting the total M number of opportunities is         respectively calculated.     -   4. Configuration is set from the number of required root seq.         per cyclic shift value.         -   A. When only one number of root seq. required for each cell             exists, configuration is set.         -   B. Case 1: when various types having the same root seq.

required per cell exist, only the case of using the largest cyclic shift value is set as the configuration, so that usage can be made up to a larger cell radius.

-   -   -   -   Case 2: only the case of using the smallest cyclic shift                 value is set as the configuration. When using this                 method, a number of sequences exceeding the required M                 number of opportunities may be generated. In this case,                 the generated sequences may be used for the purpose of a                 dedicated signature.

By using the above-described process, a similar configuration set may be configured as shown in the example of 1.1.

2. Method of Transmitting and Detecting a Cyclis Shift Value (Samples)

In specific cases, a method of using a different sequence in a cell may be required. For example, in the RACH of LTE, a low/middle mobility cell uses a generic cyclic shift, and a high mobility cell uses a restricted cyclic shift.

In case of using the generic cyclic shift, the configuration shown in Table 2 may be used without modification. The base station broadcasts the configuration through a 4-bit signaling. The terminal receives this signal and may be informed of the number of root indexes, the number of cyclic shifts per root index, and the number of cyclic shift samples that are available to the corresponding terminal. When the number of root indexes (eg. 10) used per cell is known, the number of cyclic shifts that should be used per root index for the opportunities (eg. 64), which are to be supported per cell, may be known through the ceil(M/K) (eg. ceil(64/10)=7). Once the number of cyclic shifts is known, the number of cyclic shift samples may be obtained by floor(N/ceil(M/K)) (eg. floor(839/ceil(64/10))=119).

In case of using the restricted cyclic shift, the number of cyclic shifts available for each root index may vary. In some particular cases, there may exist root indexes that cannot be used (forbidden index). Therefore, as shown in the case of using the generic cyclic shift, in this case also, the number of available root indexes in each cell is not fixed. In other words, the number of root indexes and the number of cyclic shifts that should be used in order to satisfy the opportunities, which are to be supported for each cell, may vary depending upon the cell size and the indexes used for each cell. In this case, the number of root indexes used for each cell and/or the number of cyclic shifts per root index may be signaled through additional signaling. However, this method generates additional overhead.

2.1 Same Configuration with Disregard and/or Re-Interpretation

The present invention proposes a method of using a restricted cyclic shift with another interpretation of the generic cyclic shift configuration without such additional overhead.

In the example of Table 2, when using the restricted cyclic shift, the number of root indexes per cell for the generic cyclic shift is not interpreted as the number of root indexes per cell. The number of root indexes per cell for the generic cyclic shift is merely interpreted as a parameter for calculating the number of cyclic shift samples. Similarly, when using the restricted cyclic shift, the number of cyclic shift per root index is not interpreted as its actual meaning. As shown in the case of using the generic cyclic shift, the number of cyclic shift samples may be calculated by using floor(N/ceil(M/K)) (eg. floor(839/ceil(64/10))=119). Then, the restricted cyclic shift sequence is generated by using the decided cyclic shift samples. If the restricted cyclic shift fails to satisfy the opportunity that is to be supported per cell, the root index is changed (or switched). Such method of changing the root index may be performed by using a variety of methods. For example, a method of increasing the root index as much as a specific pre-defined integer may be used. A method of deciding the amount of increase by using other information, such as cell ID or sector ID may also be used. A method of directly signaling the amount of increase may also be used, and a method of changing an index based upon a specific standard may also be used. The restricted cyclic shift is generated from the newly changed root index. This process is repeated until the restricted cyclic shift satisfies the opportunity that is to be supported per cell.

A high mobility cell may be configured without any additional signaling for the restricted cyclic shift through the disregard and/or re-interpretation of such generic cyclic shift configuration.

2.2 Different Configuration

A method of differently setting up a generic cyclic shift configuration and a restricted cyclic shift configuration may be used.

For example, the parameter for the generic cyclic shift and the parameter for the restricted cyclic shift each having the same number of configurations may be set-up differently. In this case, the terminal may use a different parameter based upon the cell mode.

For example, the number of available restricted cyclic shifts may vary depending upon the cyclic shift value. The cyclic shift values may be selected so that the number of available restricted cyclic shifts can be maximized. Such maximization may be approached in various viewpoints. For example, the restricted cyclic shift available for each root index may select numerous cyclic shift values. Such selection may reduce the complexity of the base station and the mobile terminal. By using such selection, settings may be made to gain a separate configuration for a high mobility cell. Also, such selection may be extended to low/middle mobility cells, so that a single configuration can be used.

In another example, a method of setting a restricted cyclic shift using a fixed cyclic shift section (multiples of Ncs) may be used. At this point, a larger number of restricted cyclic shifts may be generated as shown in FIG. 2, by setting the restricted cyclic shift without any restrictions, rather than setting the restricted cyclic shift using the fixed cyclic shift section. When setting the restricted cyclic shift using the fixed cyclic shift section, by selecting cyclic values having a low number increase rate, as shown in FIG. 2, so as to configure the configuration, the downsides of the restricted cyclic shift having the fixed cyclic shift section may be compensated.

[1] CCM07-037, Method for Allocating Sequence and method for Setting Circular shift Sequence Against Frequency Offset

4) Effect of the Present Invention (Design)

The present invention has the following effects.

-   -   1) The present invention decreases complexity of the base         station and the terminal, and increases a sequence reuse factor.     -   2) The present invention reduces signaling overhead.     -   3) The present invention does not require any additional         signaling for the restricted cyclic shift.     -   4) A maximum number of restricted cyclic shifts may be used.

5) Another Embodiment of the Present Invention (Design)

An embodiment of the present invention that is presently applied or highly likely to be applied in a product is selected, so as to describe in detail the operation or manufacturing method of the product itself with reference to the drawings and also to describe the overall structure of the product.

SCOPE OF CLAIMS FOR THE PATENT (REGISTRATION OF UTILITY MODEL)

This section describes the specific features of the present invention that can claim exclusive rights. This section describes the minimum structural elements (super ordinate concept) required for gaining the functional effects of the present invention (design). The end of each clause of the claims shall match with the title of the present invention (design).

-   -   1. Method of setting up the cyclic shift configuration         -   A method of configuring the configuration so that the number             of root seq. can be minimized or optimized         -   A method of configuring the configuration so that the cyclic             shift value can be maximized or optimized     -   2. A method of using information on restricted cyclic shift         through a re-interpretation of the generic cyclic shift         configuration     -   3. A method of distinguishing information on the cyclic shift         configuration as a generic case and a restricted case and using         the distinguished information     -   4. In a case of having/having no restriction in a fixed cyclic         shift section, a method of setting up a cyclic shift value so         that the number of restricted cyclic shifts can be maximized

DESCRIPTION OF REFERENCE NUMERALS FOR MAIN PARTS IN THE DRAWINGS (MARKING OF THE NUMERALS REQUIRED) DRAWINGS

A brief description of the drawings is required to be made below each drawing. 

1. A method for allowing a user equipment (UE) to select a random access channel (RACH) preamble sequence, the method comprising: acquiring at least one parameter information for a random access; and selecting the RACH preamble sequence, which is to be used by the user equipment (UE) for the random access, using the acquired parameter information, wherein the parameter information is analyzed as different values between a high-mobility mode equal to or higher than a reference value and a low-mobility mode less than the reference value.
 2. The RACH preamble sequence selection method according to claim 1, wherein the parameter information includes information associated with a circular shift value.
 3. The RACH preamble sequence selection method according to claim 1, wherein the parameter information has a length of 4 bits.
 4. The RACH preamble sequence selection method according to claim 1, wherein: the high-mobility mode equal to or higher than the reference value is called as a restricted mode, and the low-mobility mode less than the reference value is called as an unrestricted mode.
 5. A method for allowing a user equipment (UE) to generate a random access channel (RACH) preamble sequence, the method comprising: a) acquiring at least one parameter information for a random access; and b) selecting at least one parameter corresponding to the acquired parameter information from among pre-defined sequence constituent parameters, and generating the RACH preamble sequence using the selected parameter, wherein the pre-defined sequence constituent parameters are defined as a first-type set for a high-mobility mode equal to or higher than a reference value, and a second-type set for a low-mobility mode less than the reference value.
 6. The RACH preamble sequence generation method according to claim 5, wherein the parameter information includes information associated with a circular shift value.
 7. The RACH preamble sequence generation method according to claim 5, wherein the user equipment (UE) differently selects the at least one parameter corresponding to the acquired parameter information from among the pre-defined sequence constituent parameters, according to whether the UE corresponds to the first-type set or the second-type set.
 8. The RACH preamble sequence generation method according to claim 5, wherein the first-type set is called as a restricted mode, and the second-type set is called as an unrestricted mode. 